Septic system filtering arrangement, filter material and method of using

ABSTRACT

A filtering arrangement is provided for effluent from a septic tank prior to passage to a drain field or other disposal. The filtering arrangement makes use of an open-top, U-shaped filter means into which the septic effluent is conducted from the top, preferably through a T-fitting providing an open-topped channel leading into the U-shaped filter. The filter is preferably formed of an outer perforated casing and an inner lining of an open-cell-type polymeric material which effects the filtering of the effluent. The U-shaped filter is preferably suspended from the T-fitting. The arrangement provides fail-safe filtering automatically adjustable for varying flow rates and conditions of the filter. The polymeric filter medium is changed periodically to maintain efficiency.

BACKGROUND OF THE INVENTION

(1) Field of the Invention

The present invention relates generally to sewage treatment and moreparticularly to septic tank sewage treatment systems. More particularlystill, the invention relates broadly to filtering the effluent from aseptic tank system and to a filter arrangement and method for filteringseptic tank discharge prior to passage of such effluent to a drain fieldor other ground disposal system to prevent clogging or plugging of suchdrain field or system.

(2) Description of the Prior Art

Municipal treatment systems usually comprise widespread pipe collectionsystems capped by large scale treatment facilities including settling,coarse and fine filtering and possible other treatments, denoted usuallyas primary, secondary and, less frequently, tertiary treatment of thesewage. Not unexpectedly, private sewage treatment systems are usuallyrelatively more simple. One of the most widespread presently usedprivate treatment arrangements involves the use of septic holding tanksin which solids originally discharged from a waste source with theliquid portion of the sewage or waste are allowed to settle in a largetank or tanks. The overflow from the septic tank is directed into eithera so-called dry well from which it percolates into the ground, wherepassage through rock and ground strata further purifies the waste waterand removes harmful bacteria and other noxious components, or into aso-called drain field comprised of a series of perforated ceramic pipesor drains laid into shallow trenches in the ground from which the liquidportion of the sewage is absorbed or percolates into the ground where itis likewise purified by passage through the ground strata.

With the widespread exodus from city environments to suburban andsemirural environments, the use of septic systems, so called because ofthe use of a "septic tank" into which septic or bacteria-laden liquidand included solid or semisolid materials are discharged for temporaryholding and settling of the solids from the liquid material dischargedinto the tank, has been growing at a rapid rate. Such widespread use ofseptic tank systems results from the fact that only a limited number ofsuburban and substantially no rural areas have municipal or publicsewage collection and treatment systems. Other individual treatmentsystems such as basic cesspools or holding tanks, dry systems and thelike are also available, but none has become popular because of variousproblems, expenses and other inconveniences. Consequently, while thetrend for some years in the past was away from the use of the "septic"and other localized or private sewage treatment arrangements, as citiesand large towns converted their residents' sewage disposal systems fromprivate systems to large public systems, with the recent exodus of cityresidents to suburban and semirural environments surrounding most citiesbeginning soon after the second world war the trend to municipal systemshas substantially reversed. Septic-type systems are presently growingapace. Furthermore, with the burgeoning suburban and semiruralpopulation and the increasing environmental consciousness of suchpopulation, efficient and effective sewage treatment on a small scalewithin the confines of a residential property or small business orindustrial environment has assumed more and more importance.

Typically the overflow from a septic tank passes first into adistribution box before it is distributed into a drain field. The wellregulated septic tank may ordinarily discharge suspended solids in anamount of about 125 to 175 parts per million of the effluent waste waterafter it leaves the septic or sewage tank, although this will varydepending upon the amount of flow from the tank and other factorsincluding the level of solids maintained or accumulated in the bottom ofthe tank. The amount of suspended solids in the supernatent liquid tendsto increase or decrease in inverse ratio with distance from theaccumulated solids at the bottom of the septic tank. When the solidsreach an unacceptable level in the tank, an excessive amount of solidstends to be discharged with the effluent. Consequently, when the levelof solids becomes too high or the rate of included solid overflowexcessive, the tank must be "pumped" or discharged into a tank truck andthe contents disposed of. Various schemes for deciding when the amountof solids passing to the drain field is excessive have been devised,including the use of filters to catch the solids and estimate how muchis escaping into the drain field. The escape of solids into a drainfield is highly undesirable because it tends to clog up such drainfield, which, when clogged, is almost impossible to unclog and mustusually be replaced at considerable expense. In order to get penetrationof the effluent into the drain field pipe, it is desirable that theoverflow vary in intensity so that it will flow through the pipe towardsits end and be distributed along the length of the pipe rather than allstopping at one point possibly quickly clogging the system at thatpoint. So-called "dribble systems" in which the sewage overflows orcontinuously flows in a "dribble" into the drain field are usually notfavored, but instead, the effluent is preferably "dosed" into the fieldwith a slight "head" or force behind the flow. It is difficult toarrange for reliable alternating flow, however, particularly as the flowrate by the time it has been distributed into a large drain field may bevery low.

The drain field trenches, which typically comprise a trench having adepth of about 2 to 3 feet and two-and-a-half feet in width in which aceramic pipe having perforations or openings therein of about one-halfinch in diameter is laid, are filled usually with gravel or crushed rockand covered over by soil and back filled to grade level. Some systemsinvolve only a single trench leaving room for later adjacentconstruction of additional trenches when the first drain field pipeeventually clogs. Other systems can include a series of trenches withprovision to switch the effluent from one to another via a distributionjunction box to prevent saturation of any one trench. The drain trenchesin these systems are provided with time between "dosings" to regenerateby decomposing and generally disposing of liquids and small solidparticulates between use. Since a drain field is normally continuouslyreceiving a small amount of overflow solids from its disposal or wastetank, which is usually in the form of a septic tank, and the internalspaces of the drain pipes and external surrounding spaces within thetrench cannot expand, the drain field must inevitably become too cloggedto continue in operation and must be shut down and replaced. Suchinevitable shutdown can be delayed by proper operation of the system toeither (a) prevent as much as possible the escape of solid materialsinto the drain field and/or (b) by increasing the decomposition of thesolids within the drain field to encourage liquefaction of the solidmaterials into a form that can be flushed away. It has been reported insome cases, in fact, that it is desirable to have very smallparticulates escape into the drain field as this tends to providegeneral decomposition therein, actually tending to decrease or evenreverse solid buildup.

In recent years the use of so-called sand mounds has become popular oreven mandated in some areas. Sand mounds, as indicated by the name, aremounds of sand placed upon the normal surface of the ground. Smallerthan normal drain pipes are incorporated into such mounds. The drainpipes are usually one-and-one-half inches in diameter and havethree-sixteenth inch drain openings spaced at about six-foot intervals.The pipes are surrounded by crushed rock placed upon varying depths ofsand and the entire mound is then covered with soil and planted orlandscaped. The septic effluent is frequently pumped to the sand moundbecause of its higher surface location with respect to the usuallocation of a septic tank. The pump is normally run intermittently inorder to dose the drains and obtain better liquid penetration. Also acleanout pipe or connection is frequently provided at the top of themound. This pipe may be connected to a hose to flush out the drain fieldpipe or pipes. While the pipes are usually, in fact, flushed out,unfortunately the pipe orifices as well as the drain field frequentlyremain largely or partially blocked. In fact, the flushing itself mayserve to force solid particulates compactly into the sand mound reducingits permiability.

It has been recognized that it might be advantageous to filter solidmaterial from the overflow from a septic tank system (a) to decrease, oreven completely eliminate, the usual small amount of solids passing tothe drain field and/or (b) to prevent the escape of too large an amountof solids from the septic tank to the drain field during excess flowfrom the septic tank or (c) to prevent the escape of solids to the drainfield as a result of excess buildup of solids in the septic tank. Whileattractive in theory, such filter arrangements have largely not provedto be practical or effective in preventing the clogging of drain fields.This has been because the filter either interferred with the normal flowof liquid effluent to the drain field, was not easily replaced, did noteffectively filter very small particles from the effluent liquid or wasimpractically complicated or expensive.

Among the more notable proposals for the use of filters to strain ortreat the overflow from a septic tank are the disclosures of thefollowing patents:

U.S. Pat. No. 1,454,723 issued May 8, 1923 to W. T. Burtis broadlydiscloses the use of a filter arrangement with a septic tank system. Aremovable filter is comprised of a removable basket filled withalternate layers of sand and gravel to effect initial filtering of wastewater received from a cesspool, septic tank or grease trap. Thefiltering system in the Burtis arrangement is not located between acesspool and a drain field, but is located at the end of the system overa dry well into which the effluent is discharged.

U.S. Pat. No. 3,332,552 issued Jul. 25, 1967 to R. L. Zabel discloses afilter for placement directly in a septic tank. The filter is attachedto the overflow from such septic tank and is made in a tubular shapewith a series of dam and weir units in a stacked arrangement. The inletto the septic tank is in a T-shape conducting the liquid to a lowerportion of the tank about at the level of the bottom of the dam and weirfilter arrangement at the overflow side of the septic tank.

U.S. Pat. No. 3,460,675 issued Aug. 12, 1969 to R. M. Hicks et al.discloses a septic tank inspection arrangement. Hicks discloses that itis desirable to prevent solid material from escaping from the septictank and penetrating into the leach or drain field area, stopping up theleach field and destroying the operation of the field. Hicks provides aseparate trap between the septic tank and the drain field into whichsolid materials tend to flow and are collected in a receptacle in thetrap. The receptacle is provided with a handle which extends to thesurface of the trap and after removal of a cover, the receptacle can belifted up and examined to determine how much solid material is flowingfrom the septic tank to the drain field or into the trap. If no solidsare collected in the trap, the homeowner knows that none are flowing tothe drain field, while if there are solids in the trap, he knows thatsome may be flowing to the drain field and that the septic tank shouldbe cleaned to lower the level of solids before the drain field isplugged up and ruined. The trap is in the form of a removable bucket orcontainer rather than a filter. Since the test applied is qualitativerather than quantitative it is not important that all solids are notcaught.

U.S. Pat. No. 3,642,138 issued Feb. 15, 1972 to R. F. Sheda discloses afiltering tank for use with a septic system. The filtering tank has aninlet and an outlet and a series of filters formed from, for example,chopped spagnum moss as a natural filtering material. The moss isretained in cages which may be lowered by a hook into position in thebottom of the filtering chamber. A removable insulation panel is alsodisclosed across the top of the filter units to prevent the filteringunit from becoming too warm during hot weather.

U.S. Pat. No. 4,104,166 issued Aug. 1, 1978 to J. LaRaus discloses apurification tank which may be used between a septic tank and a drainfield. The purification tank in which the sewage or effluent from theseptic tank is treated with oxygen or ozone includes a multi-part filterin the bottom through which the material flows or is pumped to the drainfield. The filter is provided with a bail on the top so that it may beremoved by means of a hook from the surface by opening the top of thepurification chamber. There is also an arrangement for backwashing thefilter if necessary. The filter has a screen on the bottom over whichthere is a layer of peat gravel, covered by a layer of anthrofil, orgranulated coal, with a surmounting layer of the fine sand. Other filterarrangements may be used. It is said that the filtered fluid is so clearthat it may be used for certain low-grade purposes such as irrigation,toilet use, lawn sprinkling or the like. It is also stated that becausethe cleaned effluent contains no solids, it requires a smaller leachfield than the ordinary septic tank system. The filter is removed forcleaning or replacement periodically as it becomes contaminated.

U.S. Pat. No. 4,319,998 issued Mar. 16, 1982 to J. D. Anderson disclosesa monitor for an effluent system used between a septic tank and adisposal field. A separate monitor chamber is provided between theseptic tank and the field in which there is a screen. The screen isarranged in the monitor chamber with a vertical orientation so that whenthe screen is clean, liquid flows through it unobstructed while when thescreen becomes partially occluded by solid materials, the liquid backsup on the feed side of the screen. A suitable detector is arranged todetect any such backup of liquid, thus warning that the screen hasbecome clogged due presumably to an excessive of solid materialsoverflowing from the septic tank. This then, in effect, warns the userthat the septic tank should be cleaned.

U.S. Pat. No. 4,439,323 issued Mar. 27, 1984 to H. L. Ball discloses amethod for filtering waste water from a septic tank. Ball discloses thatmechanical filtering devices placed within septic tanks have generallybeen unsuccessful because the filter quickly became clogged by thesolids present in the tank. Various expedients for avoiding suchclogging have been used. Ball provides a hollow screen within a housingwithin the septic tank with the inlet arranged in the area of relativelyparticle-free liquid. The filter is also protected from solid materialsfloating on the surface of the water by the external wall of the filterchamber within the septic tank. The result is that Ball is able to use alarge filter area with a feed taken from a fairly restricted levelwithin the septic tank within which few solids are found which mightotherwise tend to quickly clog up the filter.

U.S. Pat. No. 4,614,584 issued Sep. 30, 1986 to M. B. Di Duca disclosesa distribution box for a drain field receiving effluent from a septictank. The distribution box is provided with a horizontal screen throughwhich the effluent from the septic tank seeps downwardly and is directedthrough suitable piping to the drain field. The filter screen, which isbasically a flat horizontal perforated plate or screen, has handles sothat it may be conveniently lifted from the distribution box when thetop of the box is removed for cleaning and the like.

U.S. Pat. No. 4,710,295 issued Dec. 1, 1987 to R. Zabel discloses aseptic tank filter basically similar to the earlier Zabel filterdisclosed in his U.S. Pat. No. 3,332,552. The improvement includes abottom cone arrangement on the filter unit which tends to collect solidmaterials and allow them to escape through a hole in the bottom of theconical bottom cap where they collect on the bottom of the septic tank.

U.S. Pat. No. 4,882,045 issued Nov. 21, 1989 to R. J. Bergh et al.discloses a selective distribution to various selected drainage fieldtrenches making use of a special distribution box. The distribution boxenables an operator to change the distribution from one drainage fieldtrench to another when a first trench becomes saturated. Along with thedistribution arrangement, Bergh et al. uses a filter arrangement on hisdistribution unit which filter arrangement prevents excess solids frompassing from the septic or sewage tank to the drain field trenches. Thecore of the distribution unit can be removed together with the filterfrom the top for cleaning. Bergh et al. also discloses the use of asensor within the distribution box to determine when the unit may beclogged.

While some of the foregoing patents may disclose operative filterarrangements for filtering the effluent from a septic tank before it isdistributed to a drain field for further treatment and disposal, nonehas proved to be the simple, effective arrangement which is required toprevent drain fields from becoming clogged. In general, the filters ofthe prior art have either been inefficient, too difficult to change orinterfere with dosing of the drain field system. The filters,furthermore, have themselves clogged too easily and quickly. The presentinventor has unexpectedly discovered and developed, by careful testingand experimentation, a filter and filter arrangement which largelyobviates the various defects of the previous arrangements.

OBJECTS OF THE INVENTION

It is an object of the present invention, therefore, to provide afiltering arrangement for use between a septic tank and a drain field orother ground disposal arrangement that is simple and effective.

It is a further object of the invention to provide a filter arrangementand filter that is more efficient than prior arrangements.

It is a still further object of the invention to provide a filterarrangement that can conveniently and efficiently be changed.

It is a still further object of the invention to provide a filterarrangement in which gravity serves to provide a continuous head on theeffluent to enhance the filtering rate.

It is a still further object of the invention to provide a filter andfilter arrangement that will allow for uneven flow from a septic tank.

It is a still further object of the invention to provide a filterarrangement in which very small particulates of solid waste materialsmay be filtered efficiently from septic tank effluent.

It is a still further object of the invention to provide a filterarrangement that can be easily cared for and changed periodically by thehomeowner.

It is a still further object of the invention to generally provide afilter and filter arrangement that is more effective than priorarrangements.

It is a still further ojbect of the invention to provide an improvedfilter material or medium for use in a septic tank filteringarrangement.

It is a still further object of the invention to provide a method offiltering for use in a septic tank drain field arrangement that is moreeffective and efficient than prior methods.

Other objects and advantages of the invention will become evident fromreview and consideration of the attached description and drawings.

BRIEF DESCRIPTION OF THE INVENTION

The present invention provides in its preferred form a filter between aseptic tank or other settling or holding tank and a ground disposalarrangement for effluent from the septic tank such as a drain fieldcomprising a hollow, open-topped, generally U-shaped or bucket-shapedouter perforated reinforcing casing mounted in a chamber between theseptic tank and drain field. The outer reinforcing casing supports afilter material lining the sides of the outer casing. The container andlining is mounted in a position such that effluent from the septic tankdrains or is pumped into the filter from the top and drains through thefilter into the chamber in which the filter is mounted from whichchamber the filtered effluent drains or overflows by gravity or ispumped into the drain field or possibly an intermediate holding tank orthe like. The preferred filter medium within the filter casing iscomprised of open-cell foam plastic material having the shape of thecasing. The casing is preferably supported in the chamber by a hangingbail arrangement, but can be otherwise supported, usually above thebottom of the chamber, in a position where it can be easily reached,removed and replaced by the owner of the disposal system. Theopen-topped, generally U-shape of the filter medium provides a maximumfilter area and provides reserve capacity which effectively adjusts tovarying flows from the septic tank without overflowing and the open topallows the effluent to overflow in an emergency from the top withoutstopping up or plugging the septic tank possibly causing a backup intothe building in which the primary drains are. The relative elevation ofthe filter with respect to the level of liquid effluent in the filterchamber provides a gravitational head upon unfiltered septic effluentand aids continuous effective filtering of the septic tank effluent.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagrammatic side elevation of a septic tank systemincorporating a filter arrangement in accordance with the presentinvention.

FIG. 2 is a diagrammatic view of an alternative embodiment of theinvention.

FIG. 3 is a diagrammatic view of a further alternative embodiment.

FIG. 4 is a partial side elevation and partial cross section of thefilter element and its preferred relation to the T-fitting upon which itis mounted.

FIG. 5 is an isometric representation of the filter and filter materialliner of the invention.

FIG. 6 is an isometric view of the filter of the invention shown in FIG.5 viewed from an alterntive angle.

FIG. 7 is an isometric view of the filter liner comprising one portionof the invention.

FIG. 8 is an isometric depiction of an alternative filter element of theembodiment of the invention shown in FIG. 3.

FIG. 9 is a diagrammatic representation of a filtering system inaccordance with the invention for a gravity-fed drain systemincorporating the present invention for a residential-type septictank-drain field system.

FIG. 10 is a cross-section of a filter assembly according to a lesspreferred embodiment of the invention having an overflow opening at thetop of the filter.

FIG. 11 is a cross-section of a preferred embodiment of the invention inwhich there is minimum clearance between the sides of the filter and thelower portion of the T-fitting and the principle fail-safe opening is atthe top of the T of the T-fitting.

FIG. 12 is an isometric view of FIG. 11 showing the relatively tight fitbetween the top of the filter and the bottom of the T.

FIG. 13 is an isometric view of a form of the filter in which the filtermaterial itself is free standing and requires no exterior perforatedcasing.

FIG. 14 shows an alternative embodiment of the invention wherein theinlet into the filter chamber and the filter passes over a depressedportion of the side of the filter.

FIG. 15 is an alternative embodiment of the invention including an inletwith an elbow bringing effluent directly into the center of the filterfrom the top.

FIG. 16 is an isometric view of an embodiment of the invention includinga fibrous matted filter element within the outer casing.

FIG. 17 shows a cross-section of the matted fiber filter shown in FIG.16.

FIG. 18 shows the exterior of a preferred filter element casing shownfrom the exterior.

FIG. 19 is a cross-sectional view of an alternative embodiment of theinvention in which the fibers of the filter material are merely loosefibers pressed generally together in the casing rather than being in theform of a distinct pressed shape or otherwise unitarily formed filterelement.

FIG. 20 shows a cross-section of an alternative embodiment of the filterof the invention in which the ends of the bail extend through the filtercasing and at least partly through the interior filter material to aidin retaining such filter material in place in the casing and in which inaddition the filter medium covers only the walls of the filter casing.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention provides an effective and efficient filterarrangement to filter the effluent from a septic tank prior to passageof such effluent to a drain field. The removal of the solid particulatesin the effluent prior to directing the filtered effluent to a drainfield or, for that matter, any other ground disposal system, preventsthe ground disposal system or drain field from becoming clogged orplugged even after extremely long periods of operation. The Applicanthas discovered that if a filter arrangement is provided in accordancewith his invention and the filter element is changed periodically, anoperation which is facilitated by the preferred mounting, that there issubstantially no build-up at all of solids in the drain pipes and adrain field therefore should last almost indefinitely. While some verysmall amount of solid may reach the drain field, this is just sufficientto encourage complete degradation and liquefaction of all solidmaterials within the system. The system, furthermore, is fail safe andaccommodates varying flows of effluent from the septic tank. Thepreferred filter material, i.e. an open-cell plastic sponge or foammaterial, has been found to quite unexpectedly be almost the idealfilter for use in septic tank effluent filtering. The material is botheasily placed within a suitable casing, extremely efficient in strainingout small particles of solids from septic tank effluent, not easilyplugged and can be readily replaced and disposed of when it hascollected a significant layer of solid materials.

As indicated above, while there have been a fair number of proposals forfiltering effluent from septic tanks and systems to remove small solidparticulates therefrom before such particulates have an opportunity toplug the drain field, none of the prior proposals has been particularlysuccessful in doing what it is supposed to do. The filter elements havebeen likely in addition to become plugged themselves with resultantinterruption of the effluent flow. Furthermore, prior arrangements havebeen, in general, not easily adjustable for varying flow.

Unexpectedly, however, the Applicant has discovered that if a filter isprovided that has a substantially open top and a significant verticalheight that an efficient fail-safe system that can accommodate fairlywide variations of effluent flow with no loss in efficiency can beprovided. The filter preferably takes advantage of a gravitational headof liquid to maintain and encourage efficient and rapid filtering andthe filter material can be readily changed and renewed. Furthermore, ifthe owner of the filter system should forget to change the filter,little detriment will result except escape of some unfiltered effluentinto the drain field system. The clogged filter, however, will not backup the system. Other conveniences, advantages and efficiencies will benoted from careful review of the following specifications and appendeddrawings.

In the figures, FIG. 1 shows diagrammatically, a septic tank 11 buriedin the earth 12, which is indicated to have a ground level 12 a. Theseptic tank 11 has a vertical-pipe type baffle 13 mounted over the endof an inlet 19 to the septic tank, and a second vertical-pipe typebaffle 15 mounted over an outlet 21 from the septic tank. These baffles13 and 15, which are shown in the form of vertical pipes having anopening at the top and bottom pierce the surface of the body of liquid24 in the septic tank and prevent a surface layer of scum 27 from beingrespectively interrupted and broken up by flow into the septic tank 11from the inlet 19 and from flowing out of the outlet 21 with effluentleaving the tank. As a result, the surface scum 27 is more or lesspermanently confined to the center of the septic tank, although theremay be some mutual interchange between the scum layer and the liquidlayer 24 in the septic tank. At the bottom of the septic tank 11, thereis accumulated a layer of solids 23. The normal water level 25 in theseptic tank 11 is indicated to be slightly higher than the lower portionof the outlet 21 allowing flow from said septic tank. It should beunderstood that this normal water level will vary somewhat with the flowof raw sewage into the septic tank through the inlet 19. When a largeflow of raw sewage enters the septic tank, the normal water level 25will tend to rise and effluent will flow from the outlet 21 throughpiping 22, to the inlet 31 of a force-pumping sump 29.

A large access cover 17 over the central portion of the septic tank andtwo smaller access covers 17A and 17B positioned in openings over thevertical baffle pipes 13 and 15 provide emergency and cleanout access tothe interior of the septic tank and prevent dirt from the earthovercover 12 from entering the tank. It will also be noted that theseptic tank 11 and the sump pump chamber 29 are shown closer togetherthan would normally be the case and the relative sizes of the twochambers or tanks are not shown to scale.

The sump 29 has an outlet 33 through which effluent is passed under theforce of a submerged pump 35. The pump 35 is operatively controlled bytwo level detectors 37 and 39 which will operate to detect a level ofliquid within the sump 29. The submerged pump 37 will be operated by asuitable electric circuit, not shown, to be activated when the upperwater level 43 of the sump is reached and will be turned off when thelower water level 45 is reached, as detected by the level detectors 37and 39.

Each level detector 37 and 39 comprises a water proof junction box 37Aor 39A provided with a float arm 37B or 39B. Circuitry to connect thelevel detectors with the pump motor 36 is conventional and does notconstitute a part of the present invention and is not therefore shown.The inlet 31 to the sump is provided with a T-fitting 49. The sump 29 isalso provided with an access cover 51, located just above the groundlevel 12a. It will be understood that upon necessity or inclination, theowner of the septic system can remove the top 51 to inspect the sump 29,particularly with respect to the filter to be described hereinafter infurther detail. Said filter is positioned broadly between the inlet tothe sump and the submerged pump 35. The T-fitting 49 on the end of theinlet 31 is preferably provided with a notch 52 in the upper arm 49A ofthe T, from which may be hung a bail or handle 59 attached to the filter53 comprising an outer casing 55 and an inner filter material 57, which,as shown in FIGS. 4 through 7, preferably comprises essentially aseparate layer within the casing 55 of the filter 53. As shown, thelower end of arm 49B of the T-fitting 49 extends part way into the upperportion of the filter 53.

The submerged pump 35 which is powered by a motor 36 on top of the pumpis preferably supported upon a stand or block 41 to attain a desiredlevel within the sump 29. The motor 36 is shown submerged in the liquidwithin the sump 29. However, in many installations the motor may belocated in the upper portion of the sump out of the liquid. The same maybe true of any electrical control apparatus for the pump. Such detailsdo not consitutue any part of the present invention. As raw sewage flowsinto the inlet 19 of the septic tank 11, such raw sewage is directedgenerally downward through the baffle pipe 13 and upon exiting from theend of the baffle the solids in the raw sewage tend to continue to sinkto the bottom and form a layer 23 of solids as shown in FIG. 1. It willbe understood that a certain amount of suspended solids will normally becontained in the liquid portion 24 of the material within the septictank 11. As one progresses upwardly in the body of liquid within theseptic tank 11, however, the amount of suspended solids tends todecrease. Consequently, as the solids layer 23 builds up in the bottomof the septic tank 11, the amount of suspended solids at any point inthe liquid above also tends to increase and the percentage of suspendedsolids in any given portion of liquid overflowing through outlet 21 willtend to rise with the rising level of the solid material accumulated onthe bottom of the septic tank 11. As the level 25 of the liquid risesabove the outlet 21 from the septic tank, the liquid septic effluentflows upwardly from the main body of liquid through the pipe baffle 15and out the outlet 21 and through piping 22 to the inlet 31 of the sumpchamber 29. Material entering the inlet 31 is discharged into theT-fitting 49 and directed downwardly by the force of gravity through thedownward arm 49B of the T-fitting 49. The liquid with suspended solidsdischarged through the arm 49B of the T-fitting enters the filter 53through the top. This liquid with suspended solids falls to the bottomof the filter 53 where it first contacts the filter element 57, which,as may be seen in FIG. 4, completely lines the sides and bottom of thefilter 53. The filter material 57, which may take several forms, but ispreferably a closed-cell plastic sponge or foam material preferably fitssnuggly within an outer casing 55 of the filter. The outer casing 55 ofthe filter 53 has small perforations in it which allow for the escape ofliquid after such liquid passes through the filter element 57. It ispreferred for the bottom of the filter 63 to be solid to add support tothe filter element so that the stream of liquid falling through thelower arm 49B of the T-fitting 49 and impacting upon the filter material57 at the bottom of the filter 53 will not rupture such filter materialwhich is effectively reinforced by the solid bottom 63. The sides of thefilter casing 55 are perforated to allow egress of the liquid after itis passed through the filter element 57. The lowest holes or orifices inthe casing should preferably directly adjoin the bottom of the casing toprovide an exit for liquid perculating through the filter material atthe bottom of the filter. Alternatively no perforate filter material mayadjoin the bottom of the filter. During passage through the filterelement 57, the liquid effluent from the septic tank has the smallsolids strained from it so that they do not progress via the pump 35 andthe outlet piping 33 to a drain field not shown. If the small solidparticles, on the other hand, were discharged to the drain field, theymight very possibly plug up such field within a fairly short period.

It has been found that a polymeric open-cell material having internalopenings of a size that will filter out of septic effluent substantiallyall solid materials greater than one thirty-second of an inch in size ordiameter does a very effective job in preventing clogging of a drainfield. Filter material that will remove smaller particulates such asdown to one sixty-fourth of an inch or less may also be effectivelyused. However, as explained elsewhere, it is believed advantageous inmost systems to allow some very small particulates to pass to the drainfield to improve digestion of other material in the drain field,including any escaped solids. Also the more restricted the openings inthe filter, the more filter area and consequently the larger an overallfilter is likely to be required and the more frequently the filter willhave to be renewed.

FIG. 2 shows an alternative embodiment of the septic tank and filterarrangement shown in FIG. 1. The same structures are identifiedgenerally in FIGS. 1 and 2 by the same reference numerals. In FIG. 2,instead of there being a sump chamber 29, there is instead a filterchamber 67. As will be understood by those skilled in the art, thepassage of the liquid effluent from the septic tank 11 in FIGS. 1 and 2is completely effected by gravity. In other words, the piping 22, whichis connected to the outlet 21 of the septic tank and to either the inlet31 of the sump chamber in FIG. 1 or the inlet 69 of the filter chamber67 in FIG. 2 passes septic effluent into the filter 53 by gravity. Theeffluent, after passing through the filter 53 in FIG. 2 tends to buildup to a level 71 within the filter chamber 67 at which point the liquidwill flow out of the filter chamber through the lateral 73 which, it maybe understood, leads to a conventional drain field. The baffles 13A and15A in FIG. 2 are in the form of plates secured at their ends to theseptic tank walls over the outlets 19 and 21 as known to the art, ratherthan the vertical pipe baffles illustrated in FIG. 1. The operation ofsuch baffles is in any case essentially the same.

It will be noted that the filter 53 in FIG. 2 is more or lesscontinuously partially submerged in the liquid effluent material withinthe filter chamber 67, at least so far as the sewage system continues insubstantial continuous use. If effluent passing through the filter 53does so quickly, therefore, there will be little head or hydraulic forceassociated with the filtering. However, if the filtering slows up,liquid will rise within the filter increasing the head or hydraulicforce and increasing the filter rate.

As will be understood, the liquid which passes into and through thefilter 53 builds up in the filter chamber 67 to the level 71 at whichpoint it flows from the outlet 73 to a drain field, not shown. Thefilter 53, therefore, as shown in FIG. 2, will be partially submerged inthe liquid within the filter chamber 67 at essentially all times. Thistends to keep the filter material from drying out, which might cause alayer of fine solids strained out of the effluent to form a resistant,almost impermiable layer on the surface of the filter element.Continuous partial submergence and moistening is particularly desirablein a filter system that may encounter fairly long periods of non-usesuch as in a vacation-home-type installation where the system may not beused while the owners are absent. On the other hand, the partialsubmergence decreases the hydraulic head available in the filter toencourage filtering if a build-up of liquid within the filter occurs. Itwill be noted that the top of the filter 53 is always maintained abovethe surface of the water in the filter chamber, at least so long as thedrain field, not shown, does not become clogged in one way or anotherand cause liquid effluent to back up within the filter chamber 67. Itwill be noted also in FIGS. 2 and 4 that if the filter itself shouldbecome clogged, liquid building up within the filter will flow over thetop of the filter between the lower portion or arm of the T and theedges of the filter. More desirably still, the sides of the filtermaterial may be pressed substantially securely against the lower portionof the T, as shown more particularly in FIGS. 11 and 12, so that thereis little or no clearance between the filter and the T. Such substantialcontact may be either direct as shown or indirect. The cup-shape orbucket-shape of the filter, provides an arrangement whereby the effluentfrom the septic tank enters the filter from the top, allows a body ofliquid to build up within the filter as the flow of the effluent fromthe septic tank increases and to then drain from the filter during aslow down in the discharge of effluent from the septic tank.Consequently, the cup or pail-shaped filter, which can be referred tobroadly as a U-shaped filter, allows for differences in flow from theseptic tank while at the same time providing a fail-safe arrangementwhereby if the flow becomes too great or alternatively the filterbecomes clogged, or partially clogged the liquid may flow over the topof the filter, or alternatively, if the opening between the fiter andthe lower portion of the T is clogged, narrow or closed, the liquid willflow from the top of the T in a fail-safe mode whereby clogging of thefilter will not cause backup into the septic tank and possibly beyondinto the laterals and pipes of the residence or industry in connectionwith which the septic tank is used. As explained above, buildup ofliquid elevation in the filter, particularly in installations where thefilter is normally maintained above the liquid level in the filterchamber, also provides additional hydraulic head upon the liquid in thefilter if desirable to increase the filtering rate.

FIG. 3 shows an alternative arrangement of the filter chamber used incombination with a septic tank in which a filter 75, instead of beingsuspended from a bail or handle, is instead supported on legs ormountings 77 at the bottom of the filter chamber, which mountings holdthe filter 75 at all times slightly above the bottom of the filterchamber. In the embodiment shown in FIG. 3, the inlet to the filterchamber enters the side of the filter 75 through an orifice in the sideof the filter better shown in FIG. 8. The filter chamber 79 in which thefilter 75 is mounted is substantially like the filter chamber 67 and isprovided with an access cover 81 comparable to the access cover 51 shownin FIG. 2. It will be understood that the filter 75 operates insubstantially the same manner as the filter 53 in that effluent isdischarged into the center of the filter and builds up if the dischargeto such filter is fast and flows away if the discharge is slow. Build-upof the septic effluent in the filter automatically increases thehydraulic head upon the effluent and will increase the filter rate.

The filter shown in FIG. 3 is, like the filter shown in FIG. 2,maintained at all times partially under the surface of the liquid withinthe filter chamber 79 to maintain the filter itself in a moistcondition. Sufficient clearance should be present from the sides so thatthe filter may be slipped into the filter chamber 79 towards the outletside so that it may be fitted over the inlet pipe 63 where it extendsthrough the side of the filter. Alternatively, a removable outlet on thepiping 69 may allow the piping to be removed, the filter 75 to bepositioned within the filter chamber and then the piping replaced withinthe opening or orifice within the filter and secured to the other pipingby screwthreads or any other convenient arrangement. While thisarrangement is not as convenient for replacing the filter as thearrangements shown in FIGS. 1 and 2, i.e. by hooking a bail or handle ofthe filter over a notch in the T-fitting, the operation of the filterassemblage is essentially the same. The same efficiencies andconvenience of discharge of the effluent into a U-shaped, cup-shapped orpail-shaped filter which easily adjusts to varying flow rates anddecreases or increases the filtering rate as may be desirable remains,together with a fail-safe option of having the liquid flow over the topof the filter if necessary to maintain the systemic flow even if thefilter should become clogged, thus preventing possible back-up of theentire system. While such emergency top flow will cause a small amountof solids to flow to the drain field, during emergency filter stoppage,this is invariably a better option than having a back-up in the systemwhich can be disastrous to the users of the system.

FIG. 4 is a side elevation of the preferred filter of the inventionshown in cross section hooked in position over the top of the T-fitting.It will be understood that a simple hook may be easily used to hook overthe bail when the access cover 51 is open to give access to the filterchamber 67. This is true with the sump chamber 29, as shown in FIG. 1and with respect to the filter chamber shown in FIG. 2. In both cases,the filter 53 can, after the bail or handle 59 of the filter is firstpicked up, preferably by a hook or the like, and moved to the side sothat it disengages from the notch 52 at the top of the T-fitting, thenbe lowered until it clears the bottom of the T-fitting, after which thefilter can be moved to the side and then brought to the surface, theinside filter element 57 removed and a new filter element installed. Theentire filter 53 may then be replaced within the filter chamber 67, orin the case of FIG. 1, within the sump chamber 21 in position on thelower end of the T-fitting after which the bail or handle is liftedbringing the filter upwardly and allowing the bail or handle to beplaced over the notch in the top of the T-fitting and after securing inthe notch, allowing the filter to slip downwardly into permanentposition.

FIG. 5 is an isometric view of the filter 53 showing openings in theside of the casing 55. The smaller, open cell structure of the preferredfilter material can also be seen in the top of the filter. The openingsin the casing 55 are numbered 83 and the smaller open cell structure ofthe filter material 57 is numbered 85. The openings in the casing maydesirably be about one-eighth inch in diameter.

FIG. 6 is an isometric view similar to FIG. 5, but is oriented to showthe bottom of the filter 53. It will be seen in particular in FIG. 6that the casing 55 of the filter preferably has a solid bottom as shown.This, as explained above, reinforces the bottom of the filter againstthe force of liquid pouring down upon its top. Otherwise, the open cellfoam filter material might tend to rupture after a period of forcesupplied by the water. Alternatively, the bottom of the filter materialcould be made thicker or could be formed from a non-porous portion ofthe plastic material. However, it is preferred to use a porous,open-cell filter material such as plastic sponge material on the bottomof the filter as well as the sides, since some filtering occurs in thebottom and liquid flows along the small space between the solid casingand the filter material and out the sides of the casing, where, asindicated above, it is preferable for the casing to have small orificesvery close to the bottom to release the liquid to the exterior.

FIG. 7 is an isometric view of the filter material prior to placement inthe casing of the filter. It can be seen that the cells or openings 85in the surface of the open cell filter material are fairly small.

FIG. 8 is an isometric view of the filter 75 shown used in FIG. 3showing the orifice 87 in the side of the filter for accomodation of theinlet pipe 69. Otherwise the filter is substantially similar to thefilter of FIGS. 1, 2 and 4-7 except for the filter being somewhat largerin diameter and lower.

FIG. 9 shows diagrammatically an entire septic and drain field systemprovided with the filter arrangement of the invention. In FIG. 9, ahouse 91 is provided as shown with sewage pipe take offs from plumbingfixtures, such as a water closest 93 in a first floor room with a washstand 95 positioned next to the water closet. Sewage pipes 97 lead fromthese plumbing fixtures and it will be understood in most cases fromother plumbing fixtures in the building to a main lateral sewage takeoff99 which leads into a inlet 101 of a septic tank 103. The septic tank103 is provided with a baffle 105 positioned in front of the inlet andwith another baffle 107 placed adjacent to the outlet 109 from theseptic tank 103. A suitable conduit or pipe 111 extends from the outlet109 to an inlet 113 to a filter chamber 115. A T-fitting 117 is providedupon the end of the inlet 113 with the top or transverse members or armsof the T extending vertically. The upper portion or arm of the T has anotch in it 119 in a position to receive the handle or bail 121 of afilter 123 which, as in the previous embodiments, is preferablycomprised of an outer casing 125 and an inner flexible or semi-flexibleinner filter element 127. As will be understood from the previousembodiments, the outer casing is preferably provided with small orificesin the side, not shown, and the filter element 127 is formed from anopen cell plastic sponge material having a cell diameter andinterconnections between the cells small enough to provide a filteringof the contents sufficient to prevent suspended solid materials receivedthrough the pipe 111 from the septic tank 103 from passing through thefilter element 127. The filtered effluent liquid which does pass throughthe filter element 127 then passes through the small holes or orifices83 in the casing and falls to the lower portion of the filter chamber115. A buildup of such liquid in the bottom of the chamber 115eventually brings or maintains the surface of the liquid essentiallylevel with the exit pipes 129 and the filtered liquid is then conductedto such exit pipes and any laterals necessary to operation of aperforated drain field pipe 133 positioned within a drain field 135. Thedrain field 135 may comprise gravel or crushed stone within a trenchsurmounted with ordinary soil 137 used as an overcover. In theembodiment shown in FIG. 9, the end of the drain field pipe 133 isconnected to a vent 139 which extends above the ordinary level of theground surface 137A. A vent improves flow through the pipe or conduit131 and into the perforated drain field pipe 133 which, as shown, hasthe holes 134 which may be approximately 1/2 inch more or less indiameter. Air vent 139, as indicated, may be desirable to encourage freeflow of liquid into the drain field and provide desirable aeration ofsuch drain field. However, it should be understood that many states andlocalities do not allow the use of a vent 139 in a drain field becauseof possible resultant atmospheric pollution and contamination. Whilesignificant odor should not arise from an effectively operating drainfield, particularly when equipped with the filter arrangement of theinvention, any odors which might arise from a drain field close tohabitation will be particularly offensive and any venting at all maythus be restricted. In such case, the ventilation of the drain field, ifany, is primarily through the surface of the ground and, in fact, it maybe desirable to have the drain field in such case closer to the surface.Gases given off from the drain field are then, in effect, filteredthrough the earth and cleansed with such filtering. There is also lessdanger that a surge in liquid effluent from the septic tank will bepassed through the drain field and out the vent contaminating thesurface of the ground. Actually, with the use of the filter chamber 115,there is also less chance that any such surge will pass from the septictank to the drain field at all. The vent 139 may also in the proper casebe designed to double as a clean out or flushing connection. Thisexpedient, however, is usually only resorted to in the case of aso-called sand mound installation.

It will be understood that the arrangement shown in FIG. 9 isproportioned and arranged so that the filter 123 is usually maintainedclear of the surface of the liquid effluent collected in the bottom ofthe tank. This arrangement provides the most rapid possible flow throughthe filter and the filter provides a very effective and efficientfiltering of the liquid effluent. It is desirable, however, when such anarrangement is used that there be sufficient use of the system so thatthe filter material is maintained in a moist condition at all times toavoid drying out and possible baking of a thin solid layer over theinside surface of the filter. Keeping the filter moist will maintain thefilter element or material in the best possible condition for long-termuse. It will also be understood that filter maintenance or replacementfrom time to time is highly desirable and eventually necessary.Replacement of the filter may be accomplished by opening the accesscover 141 and reaching down into the filter chamber 115 with a suitablehook or other grasping tool such as shown in FIG. 9 and identified bythe reference numeral 143. The access cover 141 is shown in FIG. 9removed and lying on the ground surfaces 137A and hook 143 is shownextended into the opening 149 and in engagement with the bail 121 of thefilter 123. The curved portion 145 of the hook 143 may be hooked overthe bail 121 on the filter 123 in the center of the upper leg of theT-fitting 117. While using the closed loop 147 on the hook as ahand-hold, the bail 121 may then be lifted out of the notch, 119 bettershown in FIGS. 10 and 11 which are to a larger scale, and passed to theside of the T-fitting 117 so that the filter may be moved downwardlyuntil it is disengaged from the bottom of the T-fitting 117. Once thefilter 123 is free of the end of the T-fitting 117, the filter may belifted up by the hook 143 past the T-fitting and out the opening 149normally closed by the cover plate or access cover 141. Once the filter123 is completely removed from the filter chamber, the interior filterelement or material 127 may be removed or stripped from the inside ofthe outer casing 125 and replaced by a new inner filter element ormaterial 127. The process of removing the filter 123 from the filterchamber 115 is then reversed and the filter is lowered down into thechamber supported by the hook 143 through the agency of the bail on thefilter, and after the top of the filter is engaged with the bottom ofthe T-fitting, the filter will be lifted up by the hook and the bailwill be hooked over the top of the T-fitting and insered into the notch119 to support the filter in filtering position. If the septic tank 103is operating correctly, i.e. without excessive flow, and the level ofsolids within the septic tank, which serves essentially as a largesettling tank, is not too high, the filter element or material shouldlast for a considerable time before it again will require changing.Meantime, the filter element 127 will essentially filter out or catchall the light solids suspended in the effluent from the septic tank. Thedrain field 135 will consequently not become stopped up or clogged andmay last substantially indefinitely, particularly as very light, smallsolids act as a inoculation of putrifactive bacteria which serve in awell operating system to liquify any significant solid material whichmay either get through the filter or tend to precipitate out of theliquid effluent. As a result, not only do the filter elements last forlong periods, but the filter bed or drain field is also able to continueto operate trouble free for an indefinite period.

FIG. 10 shows a less preferred embodiment of the filter 123 combinedwith the T-fitting 117. As seen in FIG. 10, the filter, which is shownin cross section, has a larger I.D. or Internal Diameter than the 0.D.or Outside Diameter of the lower portion of the T-fitting or the lowerarm of such fitting Such an arrangement has both advantages anddisadvantages. The advantages are that the opening or clearance betweenthe 0.D. of the lower arm of the T-fitting and the I.D. of the filterprovides sufficient space for the emergency overflow of liquid materialwhich may be unable to pass through the filter because of blockage orpartial blockage caused by the filtered solids which the filter isdesigned to filter out of the effluent. As seen in FIG. 12, it would besubstantially impossible, even though the filter is completely coatedwith a perculation resistant layer of solids, for a backup to occurwhich would affect the upstream septic tank. Since the open top orclearance between the inside of the filter and the outside of the arm ofthe T-fitting allows any backed up liquid effluent which may build up inthe filters due to slow filtering or a filter that requires changing orreplacement, to overflow from the filter over the top of the filter,thus preventing the filter from blocking the entire system.Consequently, if the filter becomes clogged due to inattention or othermischance, all the liquid septic tank effluent will merely overflow overthe top of the filter preventing backup in the septic tank which couldotherwise, in severe cases, reach all the way back to the originalfacilities in the building or habitation from which the sewageoriginates. If, for some reason, the space between the 0.D. of thefitting and the I.D. of the filter should become clogged by an excessiveamount of solids buildup, any excess liquid will still be free to flowout of the top or upper arm of the T-fitting. Thus, assuming the top ofthe T-fitting is lower than any openings in the system between theT-fitting and the source building or habitation, there is no way for thefilter to back up and cause a foul flood or other inconvenience in suchsource building or habitation.

FIG. 11 shows an alternative and preferred arrangement of the filterinlet assembly in which a close fit is maintained between the outside ofthe lower end or arm of the T-fitting and the upper portion of theinside of the filter. The arrangement of FIG. 11 is similar to thatshown in FIG. 10 except that a continuous cylindrical arrangement is ineffect created by a juncture between the bottom portion of the T-fittingand the upper portion of the filter. This juncture, while not completelyliquid tight, does serve a significant purpose in that it extends thevertical range in which liquid may be stored. It also by such storageincreases the hydraulic head upon the liquid septic effluent in thefilter, thus increasing the filtering rate. In other words, if a highrate of flow is established in the septic tank at any given time, suchas when people may be using several showers in a house at the same time,excess liquid may, in essence, be stored or contained in the filter notonly up to the height of the filter itself, but also in the extension ofthe T-fitting above the filter. Such arrangement, consequently, providesa reservoir of liquid which may be progressively fed to the filterduring such time as the filter may be overloaded and may be graduallydrawing down the amount of excess liquid in the filter. FIG. 12 is anisometric view of the filter arrangement shown in FIG. 11 and showsrather clearly the lack of any significant clearance between the lowerarm of the T-fitting and the inside of the filter resulting in theT-fitting essentially forming an upward extension of the filter. Suchextension, as explained, serves to provide a greater capacity thanotherwise. However, the arrangement is still a fail safe arrangementsince any excess septic effluent need merely flow over the top of theupper arm of the T-fitting to be relieved.

FIG. 13 shows an isometric representation of a filter for the inventionmade or formed essentially out of a fairly rigid material such as athick, open-cell plastic foam material having sufficient rigidity tosupport itself. It will be understood that other than for the filtermaterial having sufficient structural strength to support itself plusliquid materials inside rather than depending upon an outer casing forsupport, the essentials of the filters of FIGS. 10, 11 and 12 aresubstantially similar. The open cell plastic composition shown in FIG.13 is particularly desirable, perhaps, to provide a simple disposablefilter arrangement in which the whole filter may be merely removed fromthe filter chamber and discarded.

FIG. 14 shows a variation of the filter 75 shown in FIG. 3 as well asuse of a filter material such as shown in FIG. 13. The principaldifference between the embodiments shown in FIG. 14 and the embodimentshown in FIG. 3 is that instead of there being an orifice in the side ofthe filter casing and inner filter material, such as necessary in FIG. 3and shown more particularly in FIG. 8, the side of the filter element157 shown in FIG. 14 is cut down so that a pipe may enter the center ofthe filter so that septic effluent may be discharged directly into thefilter from over the side of the filter. The extra height of theelevated section 158 of the filter element 157 on the opposite side fromthe inlet pipe 160 serves to prevent splashing of septic tank effluentover the top of the filter against the walls of the filter chamber.Since the filter material in the elevated section 158 of the filterelement 157 has no real filtering function, this section could be formedfrom a nonperforate material either of the same composition as theperforate material or of a different material. Preferably spacers 162are used around the filter chamber to maintain the filter element 157centered in the filter chamber.

FIG. 15 shows a still further alternative arrangement similar to thatshown in FIG. 14, but in which the liquid enters the center of thefilter after passing through a feed pipe and a downwardly extending pipeor elbow which serves to direct the septic effluent directly into thecenter of the filter 163. As in FIG. 14, the filter element 163 isformed from a perforate self-supporting filter material.

FIG. 16 is an isometric view of the filter of the invention including anouter casing 123 plus an inner filter element 177 comprised of acompacted fibrous filter material such as, for example, glass wool orfiber. The individual fibers 178 may be either merely closely compactedor may be bonded more or less securely together by an adhesive or byself-adhesion effected, for example, by heating to an elevatedtemperature to lightly bond the surfaces of contacting fibers together.

FIG. 17 is a cross-section of the filter shown in FIG. 16. Since thefibers 178 of the filter are essentially lightly consolidated by anysuitable means, the filter element will usually have a fairly definitiveshape or form. Preferably such shape will be similar to the shape orform of the filter of the invention using an outlet casing to supportthe filter material.

FIG. 18 shows a preferred embodiment of the invention in which the smallorifices in the exterior of the filter casing are preferably overlainwith a plastic mesh material. This serves as an insurance that no solidparticle more than a certain maximum size pass through the filter. Thesame result can be attained by limiting the size of the openings in thefilter casing. However, it may be more efficient to have the orifices inthe casing somewhat larger in order not to constrict liquid flow toomuch and to avoid plugging. The outside layer of netting then ensures afinal sizing. The relatively thin strands of the netting, furthermore,are less easily plugged because the individual strands are thin enoughto cut any soft solid materials which are forced against them. The useof the outside netting layer 191, the use of which provides essentiallya three layer filter is generally not necessary with the preferredplastic-sponge open-cell material of the invention, but serves as a backup when fibrous filters and, in particular, unconsolidated fibrousfilter materials such as shown in FIG. 19 are used. Such filters mayhave voids or openings between some of the fibers that are oversized andthe outside netting layer then serves as useful backup to provide aminimum sizing for particulate passing through which cannot be exceededand serves to expedite flow of liquid material from the casing whileretaining, in general, all solids below a predetermined range.

FIG. 19 shows an alternative version of the filter in which the casing123 is filled with a semicompacted fibrous material such as a fiberglassmatting 193 which forms a lining on the inside of the casing 125. Whilenot as efficient and desirable as the open-cell sponge plastic filter ora consolidated fibrous filter mat, the matted fiberglass materialprovides many of the advantages of the invention, including an open-topconstruction providing a fail-safe operation, and a variable capacityproviding a more uniform operation. It will be noted that the fiberglassmatting shown in FIG. 19 is less consolidated even than the fiber-typefilter elements shown in FIGS. 16 and 17.

FIG. 20 shows an alternative version of the invention which issubstantially similar to the embodiments shown in FIGS. 10 and 11 but inwhich the ends 197 of the bails extend completely through the outercasing as well as the inner filter material near the top of such filtermaterial and aids in holding such filter material in position within thecasing.

FIG. 20 also illustrates an embodiment of the filter of the invention inwhich the filter medium adjoins only the sides of the filter casing, thebottom being left open. It will be understood that the bottom of thecasing is imperforate. Basically the filter medium is in the form of acylinder 127A of filter material rather than of a cup. It is necessaryin such case, however, for the filter medium or material to be pressedtightly against the bottom of the filter casing to ensure no leakage ofsolids occurs around the bottom. Such tight fit is aided by theprotruding bails, which, however may usefully support the filtermaterial also when such material has a bottom. Various flangearrangement, not shown, may be used to prevent leakage around the endsof the filter. As may be recognized, the filter material need also notbe a continuous cylinder on the sides, but could be discontinuous if theproper precautions to prevent leakage about the ends and sides and tohave the filter material over all perforated portions of the filtercasing are taken. In general, it is advantageous to have as much of thearea, or at least the sides of the filter, devoted to filtering aspossible, however.

It will be seen from the above that by use of the inventor'sarrangement, a very efficient, yet practical and simple filterarrangement is provided that will filter efficiently almost all smallsolid particles from septic effluent so that they will not flow throughto the drain field and over a period of time, stop up such drain field.A very minor portion of the solid particles may pass through the filterarrangement. However, it has been found that this is not a detriment,since a very small portion of solid particles may actually increase theefficiency of the operation by serving as initiators for furtherputrifactive degradation and liquidfaction of any solids that may reachthe drain field. It has been found by the present inventor in thisregard that the use of his open-cell, all-plastic sponge filter materialis particularly efficient and effective in filtering out of a septiceffluent substantially all solid or semi-solid particulates that maygive any difficulty in a drain field. The size of the opening betweenthe cells of the open cell filter material may be selected to filter outalmost any size range of solids desired.

The arrangement of the invention is simple and easy to replace and isfail safe because of its open-top structure which allows excess effluentto escape rather than backing up into the original sewage disposallaterals and other piping from the original site of the waste plumbingfixtures from which the sewage originates. As indicated, the open-topform of the invention makes the filter apparatus essentially fail safeand prevents backing up of sewage and other sewage effluent from thesedimentation or septic tank into the plumbing fixtures from which thesewage originates. The cup or bucket shape of the filter, meantime, alsoprovides a very desirable arrangement in which the variable flow ratefrom the original plumbing fixtures may be adjusted for in the filter toprovide a more even flow rate. In times of high flow, excess effluent isin effect stored within the filter, while such excess fluid storedwithin the filter itself is, during times when the flow of effluent fromthe septic tank is low, allowed to gradually flow out of the filter intothe system, meanwhile very effectively filtering the small particles ofsolids from the liquid portion of the effluent. The more fluid is storedin the filter, moreover, the greater the hydraulic head upon such liquidmaterial and the faster will be the flow from the filter. Not only isthe arrangement of the filter much superior to prior arrangements offilters and septic tank systems, but the new material from which thefilter material is formed, i.e. open-cell plastic film material, is muchmore efficient for a septic tank sewage operation than other filtermaterials previously used. It has been found that the efficiency of thenew filter material and the handling of sewage-type waste waters isseveral orders of magnitude better than dealing with the removal ofsmall particulates from a waste water by means of previously known andused materials.

In this application and the accompanying claims the following terms havethe hereinafter assigned meanings:

The term "septic tank" means any settling tank or other apparatus inwhich solids are settled or concentrated at a restricted location insuch apparatus by the action of gravitational or other similar force.

The terminology "effluent" or "septic effluent" unless otherwiseindicated means a liquid, plus any suspended or included solids, deriveddirectly or indirectly from an overflow from a septic tank.

The terminology "ground disposal" means the disposal of waste water andany included solids into the ground by absorbtion or perculation intothe ground both vertically and horizontally as appropriate such as bythe use of a drainage field, dry well or other perculation enhancingarrangement.

The terminology "T-fitting" or "T-type fitting" means an arrangement ofconduits or pipes in which a main conduit adapted for flow conduction iscapped or crossed at one end by a second conduit which connects to andcrosses the first conduit, the two ends of which cross conduit arenominally open to the passage of liquid flowing in the main conduit. Inthis application the cross conduit when connected to a fitter isunderstood to be generally vertically oriented and the upper section ofsuch cross conduit is denoted as the upper arm and the lower section ofsuch cross conduit is denoted as the lower arm.

The terminology "open cell plastic sponge material" or "open cellplastic foam material" means respectively either a flexible or a stiffresin-type polymer material injected or otherwise provided with a gasduring consolidation or curring to form bubbles or generally roundedopenings within the polymer material, said bubbles remaining as discreteopenings in the plastic after consolidation, solidification, hardeningor curring, and at least a substantial number of said bubbles beinginterconnected in a manner such that a liquid may move from one bubbleto another, the interconnecting openings between the bubbles or openingsbeing largely smaller in transverse dimension than the bubbles orgenerally spheroidal openings that are interconnected by saidinterconnecting openings.

The term "consolidated" means brought together into a more or lessdistinct collection or body such as by manual or mechanical compression,molding or the like force or movement. The consolidated material mayhold more or less together either statically by form or mechanicalentanglement or by molecular adhesion through chemical or other means orlike changes effecting adhesion or consolidation.

The term "U-shaped" or "concave" when used in the context of a filter,means a filter having generally the shape of a cup, bucket, water glassor other such container having a flat or sloping bottom and upwardlyinclined sides surrounding the bottom, which sides will usually, but notnecessarily, be circular in outline. A cylindrical or frustoconicalshape is included, including various upwardly or laterally curved wallsections and bottom sections. The filter will be open-topped or at theleast be provided with a liquid overflow outlet at or near the top incase of backup of liquid in the filter. Generally, the filter will havea greater height than diameter, but not necessarily.

While the present invention has been described at some length and withsome particularity with respect to several described embodiments, aswell as the best mode now known to the applicant, it is not intendedthat the Applicant's invention should be limited to any such particularsor embodiments or to any particular embodiment, but is to be construedbroadly with reference to the appended claims so as to provide thebroadest possible interpretation of such claims in view of the prior artand therefore to effectively encompass the intended scope of theinvention.

I claim:
 1. In an effluent disposal system including an upstream septictank, a downstream ground percolating disposal means and an overflowconduit conducting effluent from the septic tank to the ground disposalmeans, an effluent filtering arrangement between the septic tank and thedisposal field comprising:(a) a chamber serving at least in part as afilter chamber having an inlet connected to the conduit conductingeffluent from the septic tank and an outlet connected with the conduitleading to the disposal field, (b) a filtering means having a generallyupwardly extending side or sides and a bottom connecting said sides atleast a portion of at least one of which sides and bottom is perforate,(c) a filter medium means interposed in the perforate portion of thefiltering means to filter solids from effluent passing through theperforate section, (d) conduit means connected with the inlet todischarge effluent from the septic tank into the top of the filteringmeans, (e) the depth of the filtering means being sufficient to at leasttemporarily retain a pool of liquid therein sufficient to provide avariable depth pool of liquid adjacent the filter medium to adjust thefilter rate of the filter means to varying flows, (f) the upper portionof the filter means being open to allow for overflow of effluent fromthe filter means in case the filter medium becomes clogged or the flowrate remains greater than the feed rate over an excessive period of timedue to partial occlusion of the filter over time, (g) support means toretain the filter means upright in the filter chamber with theperforated portion unoccluded by any contiguous structure, and (h) thesupport means being arranged and constructed together with the filteringmeans to facilitate withdrawal of the filter medium means through anopening in the upper portion of the chamber and substitution by areplacement filter medium means.
 2. An effluent disposal system inaccordance with claim 1 wherein the filter medium means is comprised ofa fibrous filter material.
 3. An effluent disposal system in accordancewith claim 2 wherein the fibrous filter material has a consolidatedstructure in which at least some of the fibers are adhered to at leastsome other contiguous fibers.
 4. An effluent desposal system inaccordance with claim 3 wherein at least the majority of the fibers ofthe fibrous filter material adhere to other fibers with which they arein contact.
 5. An effluent disposal system in accordance with claim 2wherein the fibers are consolidated only by mechanical means and do notsubstantially adhere to each other.
 6. An effluent disposal system inaccordance with claim 1 wherein the filter medium means is comprised ofan open-cell plastic sponge-like material.
 7. An effluent disposalsystem in accordance with claim 6 wherein the bottom of the filter meansis imperforate.
 8. An effluent disposal system in accordance with claim1 wherein the filtering means and the filter medium means are unitaryand comprise a stiff, generally U-shaped plastic means having anopen-cell structure throughout at least a substantial portion thereofextending from an inner wall to an outer wall constituting a filteringwall.
 9. An effluent disposal system in accordance with any of claims 1,2, 6, and 8 wherein the support means for the filter means and filtermedium supports the filter means by suspension in the filter chamber bymeans comprising loop means interengaged with a hook-type means.
 10. Aneffluent disposal system in accordance with claim 9 wherein thehook-type means comprises notch means associated with an upper arm ofthe cross member of a T-fitting, the lower arm of which cross memberextends into the upper portion of the filter medium and means and theloop means comprises a bail on the filter.
 11. An effluent disposalsystem in accordance with any of the claims 1, 2, 6 or 8 wherein theconduit means connected with the inlet of the filter chambers includes aT-fitting having the cross conduit oriented substantially vertically,the upper arm of which T-fitting is open and the lower arm of which isarranged to conduct septic effluent into the upper portion of thefiltering means.
 12. An effluent disposal system in accordance withclaim 11 wherein the outside of the lower arm of the T-fitting issubstantially at least indirectly in contact with the filtering means atleast through the filter medium means.
 13. An effluent disposal systemin accordance with claim 2 wherein a perforated portion of the filtermeans is the bottom and the filter means is supported above the bottomof the chamber.
 14. An effluent disposal system in accordance with claim13 wherein at least a portion of the sides of the filter means isperforated and a separate filter medium abuts the perforated section.15. An effluent disposal system in accordance with claim 14 wherein thefilter means is supported from a bail hooked over a notch in the top ofa T-fitting serving as the inlet into the chamber.
 16. A septic tankeffluent filtering apparatus comprising:(a) a below-ground-level chamberarranged and adapted to receive septic tank overflow from a septic tankthrough a conduit, (b) a T-fitting attached to the conduit and extendingat least partially into the chamber from the conduit, (c) a concavefilter supported under the end of a lower leg of the T-fitting with theopen end of the concavity facing upwardly toward the lower leg of theT-fitting, (d) the concave filter having a diameter and heightsufficient to receive without over-flowing the normal surge from theseptic tank incident to operation of plumbing facilities attached tosewage connections leading into the septic tank, (e) said concave filterhaving a perforated portion effectively covered with a restrictedopening filter material through which septic effluent passes whileleaving solid material upon the filter material, and (f) means to removethe filtered effluent discharged into the sunken chamber from suchchamber to subsequent effluent treatment and disposal means.
 17. Anapparatus in accordance with claim 16 wherein the concave filter issupported upright in the chamber by suspension additionallycomprising:(g) suspension means attached to said filter and extendingabout securing means associated with the T-fitting.
 18. An apparatus inaccordance with claim 16 wherein the securing means is stabilized on theT-fitting by means of a depression in the top of said T-fitting and thesuspension means is a bail which fits into the depression.
 19. Anapparatus in accordance with claim 18 wherein the filter means isperforated on both the sides and the bottom.
 20. An apparatus inaccordance with claim 18 wherein the filter is suspended clear of anynormal accumulation of effluent in the chamber.
 21. An apparatus inaccordance with claim 19 wherein the configuration and dimensions of thefilter and the chamber, including the exit from the chamber, is suchthat the filter is partially, but not wholly, submerged in effluentwithin the chamber.
 22. An apparatus in accordance with claim 16additionally comprising:(g) support means mounted upon the bottom of thechamber upon which support means the filter means is supported.
 23. Anapparatus in accordance with claim 22 wherein the filter means isperforated on both the sides and the bottom.
 24. An apparatus inaccordance with claim 23 wherein the filter means is supported clear ofthe normal effluent level in the chamber.
 25. An apparatus in accordancewith claim 23 wherein the configuration and dimensions of the filter andthe chamber, including the exit from the chamber, is such that thefilter is partially, but not wholly, submerged in effluent within thechamber.
 26. An apparatus in accordance with any one of claims 16, 17,18, 20, 21, 22, 24 or 25 wherein the restricted opening filter materialcomprises a polymeric open-cell material.
 27. An apparatus in accordancewith any one of claims 16, 17, 18, 19, 20, 21, 22, 23, 24 or 25 whereinthe restricted opening filter material is a fibrous material.
 28. Amethod of filtering septic tank effluent between a septic tank and aground disposal means comprising:(a) passing the septic effluent into afiltering chamber through conduit means leading directly into the upperportion of an open-topped, generally U-shaped, perforate filtering meansat least lined with an open-cell polymeric replaceable filteringmaterial, (b) passing the septic effluent through the open-cellpolymeric material to filter solid materials more than a predetermineddiameter from the septic effluent, (c) collecting the filtered effluentin the lower portion of the filter chamber and conducting to said grounddisposal means, (d) refraining from actively inhibiting unfilteredseptic effluent overflowing from the top of the U-shaped filtering meansif such filtering means should become at least partially occluded, (e)monitoring the build-up of solid materials upon the inside of the filtermedium, and (f) upon the deposit of sufficient solid material upon theinside of the filter medium to detrimentally decrease filtering to adegree which may cause detrimental build up of the normal level ofeffluent in the U-shaped filtering during filtering, removing the usedpolymeric replaceable filtering material and replacing with freshpolymeric filtering material.
 29. A method of filtering septic tankeffluent in accordance with claim 28 wherein only a polymeric lining ofthe filtering means is removed and replaced.
 30. A method of filteringseptic tank effluent in accordance with claim 28 wherein substantiallythe entire U-shaped filter means is comprised of open-cell polymericmaterial and is removed when a filtering rate-retarding amount of solidmaterial is deposited upon the interior of the U-shaped filter means anda replacement filter means is substituted for said removed filter means.31. A filtering apparatus for filtering solids from a septic tank beforepassing said effluent to a ground disposal means comprising:(a)generally U-shaped filter means designed and constructed for supportwithin a filtering chamber in a position to receive effluent from saidseptic tank via conduit means into the interior of said filter, (b) saidfilter means including:(i) an outer perforate casing, (ii) an innerfiltering medium comprising a polymeric open-cell polymeric materialhaving openings between the cells having a size on the average, not morethan one-thirty second of an inch forming a lining in the perforatecasing and generally supported by said casing, (c) a support means forsaid filter means, and (d) a T-fitting means associated with the filtermeans arranged and constructed for receipt of effluent from a conduitconnected with a septic tank into the trunk of the T and then throughone arm of the cross conduit of the T which is vertically oriented intothe top of the filter means to direct effluent into said filter means,the other arm of the T being open and available for emergency overflowof effluent in case of at least partial blockage of the filter.
 32. Afiltering apparatus in accordance with claim 31 wherein the lower arm ofthe T-fitting and the upper portion of the filter means aresubstantially in at least indirect contact, sufficient to at leastimpede the passage of effluent between or through the region of contactto decrease the dynamic pressure of the effluent against the innersurface of the filter means.